1. Field of the Invention
This invention relates to an inorganic film base plate, which comprises a base plate and an inorganic film having been formed on the base plate. This invention also relates to a process for producing the inorganic film base plate. This invention further relates to a piezoelectric device comprising an inorganic film, which contains a piezoelectric material, and electrodes for applying an electric field across the inorganic film, the inorganic film and the electrodes being formed on a base plate. This invention still further relates to an ink jet type recording head and an ink jet type recording apparatus, which are provided with the piezoelectric device.
2. Description of the Related Art
Piezoelectric devices provided with a piezoelectric film, which has piezoelectric characteristics such that the piezoelectric film expands and contracts in accordance with an increase and a decrease in electric field applied across the piezoelectric film, and electrodes for applying the electric field in a predetermined direction across the piezoelectric film have heretofore been used as actuators to be loaded on ink jet type recording heads, and the like. As piezoelectric materials, there have heretofore been known composite oxides having a perovskite structure, such as lead zirconate titanate (PZT).
As described in, for example, Japanese Unexamined Patent Publication No. 2005-153353, it has been reported that the piezoelectric film is not constituted of a continuous film and is constituted of a pattern composed of a plurality of regions (ordinarily, protruding regions), which are mechanically separated from one another, such that the expansion and contraction of the piezoelectric film may occur smoothly and such that a large displacement quantity may be obtained. Each of regions of a piezoelectric film, which regions are mechanically separated from one another and are capable of undergoing independent expansion and contraction, will herein referred to as the piezoelectric region.
In order for a desired strain displacement quantity to be obtained, the piezoelectric film is formed so as to have a thickness falling within the range of approximately 1 μm to approximately 5 μm. The thickness of the piezoelectric film falling within the aforesaid range is larger than the thickness of each of the electrodes, and the like, on the order of nanometers (e.g., the thickness of 200 nm). As described in, for example, U.S. Pat. No. 6,436,838, heretofore, the piezoelectric films, such as the PZT films, are ordinarily subjected to the patterning with dry etching processing.
Ordinarily, the dry etching processing is known as an isotropic etching processing. However, PZT, or the like, is a material which is hard to etch. Also, the piezoelectric films are thicker than the electrodes, and the like, having a thickness on the order of nanometers. Therefore, the drying etching processing of the piezoelectric films is harder to perform than the processing of the electrodes, and the like. Accordingly, in cases where the dry etching processing is performed on the piezoelectric films, perfectly an isotropic etching is not always capable of being achieved, and end faces of the piezoelectric regions having been formed with the dry etching processing are apt to have taper shapes.
In the cases of the ink jet type recording heads, such that enhanced image quality of recorded images may be obtained, a high level of uniformity in piezoelectric characteristics of the plurality of the piezoelectric regions constituting the piezoelectric films is required of the ink jet type recording heads. However, with the dry etching processing, which yields the piezoelectric regions having the taper end face shapes, it is not always possible to accomplish accurate matching of angles of the end faces of the plurality of the piezoelectric regions. Hereafter, there will be the possibility that the adverse effects of a variation in piezoelectric characteristics, which variation occurs due to a variation in shapes of the piezoelectric regions, upon the image quality of the recorded images will not be capable of being ignored. In cases where the accuracy of the end face shapes of the piezoelectric regions is taken into consideration, the end face shapes of the piezoelectric regions should preferably reliably take shapes approximately normal to a surface of a base plate, on which the piezoelectric regions are formed.
Also, with the piezoelectric films, such as the PZT films, the problems are encountered in that, since the dry etching processing is hard to perform due to the material characteristics and the thicknesses of the piezoelectric films, a long time is required to perform the patterning. Further, with the dry etching processing, since a vacuum process is necessary, the cost is not capable of being kept low.